Effects of aerobic and strength exercise on motor fatigue in men and women with multiple sclerosis: a randomized controlled trial.

OBJECTIVE: To investigate the effects of aerobic and strength exercise on motor fatigue of knee flexor and extensor muscles in subjects with multiple sclerosis (MS). DESIGN: A randomized controlled trial. SETTING: At Masku Neurological Rehabilitation Centre, Masku, and the Social Insurance Institution, Research Department, Turku, Finland. SUBJECTS: Ninety-five MS patients with mild to moderate disability were randomized into exercise group (n =47) and a control group (n =48). INTERVENTION: Participants in the exercise group attended in a supervised exercise period of three weeks, which was followed by a home exercise programme lasting for 23 weeks. Patients in the control group continued with their normal living. OUTCOME MEASURES: Motor fatigue of knee flexor and extensor muscles was measured during a static 30-s maximal sustained muscle contraction. The decline in force (Nm) during the 30 s was recorded, and a fatigue index (FI) was calculated. Subjective fatigue was measured by using the Fatigue Severity Scale (FSS). The Ambulatory Fatigue Index (AFI) was calculated on the basis of a 500-m walking test. Assessment took place at baseline, at the third week (not for the control group) and at the 26th week. All outcome variables were analysed, men and women together, and some interesting contrasts were analysed by gender. RESULTS: Associations were observed with changes in extension FI and Expanded Disability Status Scale (EDSS) score and mean extension torque (Nm), but not with changes in FI and aerobic or strength exercise activity, mean AFI, mean FSS or in mean knee flexion torque. AFI was decreased in all subject groups (p =0.007). Motor fatigue was reduced in knee flexion (p=0.0014) and extension (ns) among female but not in male exercisers after six months of exercise. The exercise activity of women was 25% higher than that of the men. CONCLUSIONS: Six months of exercise reduced motor fatigue in women, but not in men.

Assessment of muscle strength and motor fatigue with a knee dynamometer in subjects with multiple sclerosis: a new fatigue index.

OBJECTIVE: To measure muscle strength and motor fatigue with a knee dynamometer and to assess the intra-rater reliability of measurements for maximal isometric extensor and flexor torques and the reliability of a new fatigue index (FI) in patients with mild to moderate multiple sclerosis (MS). DESIGN: Repeated assessments with one-week intervals. SETTING: The Masku Neurological Rehabilitation Centre, Masku, and the Social Insurance Institution, Research Department, Turku, Finland. SUBJECTS: Twenty-eight MS patients. OUTCOME MEASURES: Maximal isometric torque during 5 s and fatigue of knee flexors and extensors during isometric contractions of 30 s were assessed. A new FI was established and compared with the two previously used indices (FI1 and FI2). All three indices are based on the calculated area under the force versus time curve (AUFC), with FI1 using the 30-s recording time in its entirety and F2 omitting the initial 5 s in the calculation. In the new fatigue index (FI3), the time point of maximum (TPM) torque achieved by the subject is used as the starting point in the calculation. The patient's subjective fatigue was measured by Fatigue Severity Scale (FSS). RESULTS: The intraclass correlation coefficient (ICC) was 0.97 in maximal isometric torque measurements. FI3 showed good intra-rater reliability (ICC =0.68-0.86). None of the fatigue indices correlated with FSS. CONCLUSIONS: Maximal isometric torque and motor fatigue of knee flexor and extensor muscles can be reliably measured using a knee dynamometer in MS patients. The new FI proved to be a reliable model for MS patients.